1. Field of the Invention
The invention is generally related to the laying and installation of underwater and offshore pipeline and more particularly to the structure attached to the pipe end line that is used to position the pipeline for tie-in, disconnection and/or reconnection of the pipeline with another line.
2. General Background
Underwater (river, lake, or reservoir) and offshore/marine pipelines are installed by the use of a variety of techniques such as S-lay, reel-lay, or J-lay on the surface or bottom towed. In the S-lay and J-lay techniques, a length of pipe is added to the upper end of pipeline that has already been installed, the vessel moves forward along the pipeline path to install the new section of pipe, another section of pipe is added, and the process is repeated until the entire pipeline has been installed. In the reel-lay technique, the sections of pipe are welded together and wound onto a large reel on a vessel. The pipe is then unwound from the reel, straightened, and laid offshore as the vessel moves along the predetermined path for the pipeline. In surface or bottom towed operations, the onshore prefabricated end tested length is launched and tracked to the final scheduled location.
Pipelines tie in with other connections such as a manifold or a xe2x80x9cTxe2x80x9d or xe2x80x9cYxe2x80x9d-connector for branch arrangements or a wellhead that produces oil or natural gas. At such connections, it is essential that the pipeline be positioned at or above the sea floor and in the proper orientation for successfully making the necessary connection. To support the pipeline at or above the underwater sea floor, the pipeline head, or end line is typically supported by a bottom closed support structure that spreads the load of the pipeline across an area of the underwater sea floor.
Because a pipeline may rotate or twist about its longitudinal axis during its installation and descent to the sea floor, it is possible that the end line support structure, as well as any underwater connecting aids on the pipeline and connector guides, may not land on the sea floor in the proper orientation. The result is that the support structure does not lay flat on the sea floor and thus does not provide proper support to the pipeline on the sea floor. This causes difficulty in subsequent tie-in, disconnection, and/or reconnection to the pipeline because of improper orientation of fittings and/or connecting aids.
The invention addresses the above need. What is provided is a rotatable pipeline end termination. A conduit is attached to an end of the pipeline. One or more collars are attached to the conduit. A ring is rotatably received on the collar. A flat bottom closed pipeline support structure such as a mud mat is attached to the ring. The ring may be free floating for rotation or may be manually or remotely activated to rotate the termination to the correct orientation.